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Measuring current using CT and microcontroller

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prasad70

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Can some please explain how a current transformer can be interfaced to a pic to measure current from 0- 100A.

regards
 

Here is a good example of how to do it using a series shunt resistor.

OpampCircuit.jpg
 

hi,
after the CT you put rezistor as a load, a precision rectifier + some signal conditioner circuit, and you can conect directly the microcontrollers ADC.
;-)
 
This circuit is completely functional with DC and AC measurements.
If you want to sense frecuency and peak voltage (proportional to the current in the load) you can try this technique of an application note from Atmel: http://www.atmel.com/Images/doc2508.pdf
So you can have an interrupt each time the sinusoidal signal crosses zero. Using simple maths you can use the microcontroller ADC to save the magnitude of the voltage exactly at the point to measure the maximum value (peak). And there you have, a very cheap AC/DC current sensor.

Circuit.JPG
 

Thank you all for sharing your knowlege. What I want is to use a cuurent transformenr to measure AC current rangiung from 0- 100A while keeping total isolation from main circuit. Think I can use Current transformer, burdon resistor and precision ractfier cisrcuit to get current value. Does average voltage output of precision rectfier give proportional value to the current flowing in the conductor ?
Do I need to sample voltage output of OP amp and get RMS value ?

thks
 
100A is a lot to use in an invasive sensor. I would go using Hall-effect current sensors (It is also much more safer).
 
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